Wednesday, April 20, 2022

I Wish My Eyes Were Three Feet in Diameter

 Because then my irises (iriii?) would be 12" light gatherers.  (Getting dates might have been difficult, except in Area 51.)  All of this lead-up to these 2x54 ultrawide angle binoculars.  If you know much about optics, you know that light gathering increases with the square of the increase in diameter.  A young person under a very dark sky has irises that dilate to about 7mm.  These binoculars will increase the gathered light about 8x, so you will see stars down to about magnitude 8.5.  Old eyes like mine will get at least a 2 1/2 magnitude gain.  I am going to buy these once I have paid off the new tires the Jaguar needs.  (Tax time was not as bad as usual, but still four figures.)  There is also no hurry.  It will be a couple months before we get clear skies.

There are also 2x40 and 2.1x42 versions.  The SVBONY 2.1X42 version is threaded to use various filters (such as the kind that filter out mercury street light frequencies).

Thanks for the corrections.  The smaller and cheap versions might give most of the brightness advantage.

Vixen SG 2.1x42mm are similar but made in Japan. 


  1. Clayton, remember that the effective light gathering power of a telescope depends on your iris diameter times the magnification. So a 2x54 binocular would only have an effective objective of 2 times 7mm (i.e. 14mm, not 54mm). So, why 54mm? To get a wider field of view. This is a pair of Galilean telescopes, a non-inverting design that would have a terribly narrow field of view otherwise. And it will only give you a 2^2 or 4 times increase in brightness, i.e. 1.5 magnitudes.

    1. The SVBONYs would give the same brightness gain in exchange for a somewhat narrower field of view.

  2. Except that binoculars, telescopes and the like do not gather light. They transmit and magnify whatever falls on the objective lens.